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Don't sit in twilight all day!

An artikel by Jan Denneman for the Led professional Review

Life on earth has developed over hundreds of millions of years under the influence of the 24-hour rhythm of the sun’s energy, light and darkness. In order to cope with this, 24-hour rhythms have also developed in all forms of life: the so-called circadian processes. These processes are the oldest and most fundamental processes that make life possible. Life uses the light of day and the darkness of night to keep in sync with the rhythm of the planet.

Humankind, our species, Homo Sapiens, has been around for about thirty thousand years. For most of our relatively short history, we were outdoors during the day. As hunters and gatherers, we lived off the edible food we found outdoors. So we automatically got enough daylight every day. This ensured that our circadian rhythms kept pace with the time of day. In recent centuries, however, humans have increasingly begun to live indoors. Since the industrial revolution, this transition has been very rapid. We now spend most of our lives indoors (90%).

Few people realize that the intensity of light indoors, even with electric lights on, is comparable to or less than the intensity of daylight outside at the time of sunrise and sunset. So we are inside all day in the twilight! During the day the intensity is much too low and at night much too high compared to the light outside. Our bodies cannot interpret the constant signals of twilight properly and our circadian rhythm gets out of sync with real time. Every day that we do not get enough daylight, our personal circadian rhythm lags behind by about 15 minutes. After just a few days, our personal clock can be more than an hour behind. This has consequences for our health. When you go to bed, you fall asleep because you are tired, but your body is not yet ready for a good deep sleep. Due to superficial sleep, your body does not recover sufficiently at night and you do not wake up rested. During the day you are less fit than you would like to be and your mood becomes gloomy.

“Good light is just as important for your well-being and health as good nutrition and sufficient exercise.”


If you recognize these symptoms, it may indicate a disrupted rhythm due to a lack of daylight or light at the wrong time. Many people suffer from this.

The best way to stay in rhythm is to be outside a lot every day. A few hours of morning light is especially good. Daylight is always the right light for our biological clock, and our body responds positively to it. If you can’t be outside, make sure you are inside close to a window during the day, less than a meter away and facing the window. Otherwise, your body will still only experience twilight.

If this is not possible, make sure you have good lighting that mimics daylight as closely as possible. For this, it must have the same rhythm as daylight: dynamic in intensity and light color. During the day it must be sufficiently strong, at least five times stronger than what you are used to. Otherwise your biological clock will not react properly. Good light, i.e. the right light at the right time, can change your life. A lot of light during the day and cozy, dimmed light at night. You will notice that you wake up rested, can handle more during the day and are less likely to feel depressed. Good light is just as important for your well-being and health as good nutrition and sufficient exercise.

At Light & Building, we will see many innovations in the field of energy efficient and smart lighting. It will be up to the lighting manufacturers to actually bring these innovations to market and provide the billions of people who sit inside, in the twilight, every day with good light.



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